Geological setting of the Lonnie niobium deposit, British Columbia, Canada Simandl, G.J. 1,2,a , Reid, H.M. 1 and Ferri, F. 1 1 British Columbia Geological Survey, Ministry of Energy, Mines and Natural Gas, Victoria, BC, V8W 9N3 2 University of Victoria, School of Earth and Ocean Sciences, Victoria, BC, V8P 5C2 a corresponding author: [email protected] Recommended citation: Simandl, G.J., Reid, H.M., and Ferri, F., 2013. Geological setting of the Lonnie niobium deposit, British Columbia, Canada. In: Geological Fieldwork 2012, British Columbia Ministry of Energy, Mines and Natural Gas, British Columbia Geological Survey Paper 2013-1, pp. 127-138. Abstract The Lonnie Nb deposit lies along the Wolverine fault, which is related to the Manson Creek fault system. It is the third-most developed Nb prospect in British Columbia. Unlike the larger Aley Carbonatite and Upper Fir deposits, where the Nb and Nb+Ta zones are carbonatite-hosted, historical work suggests that the highest Nb grades at the Lonnie complex are in quartz-free feldspathic rocks. The carbonatite (metacarbonatite) zones also contain significant concentrations of Nb. Limited sampling carried out in 2012, including 12 samples from the Lonnie deposit, agrees with the historical findings: the highest Nb value (>2500 ppm) is from one of three quartz-free feldspathic samples; the next highest values (1670 and 1210 ppm) are from two of five carbonatite samples. The 2012 sampling indicates that the metacarbonatites have chondrite-normalized REE patterns that are similar to the quartz-free feldspathic rocks, fenites, and nearby limestone; however, they have the highest REE concentrations. Fenitization extends for more than 30 metres southwestward into the host rock, perpendicular to the strike of the Lonnie mineralization and projection of the Wolverine fault. Carbonatite emplacement predates 4 periods of tectonic activity and the metamorphic peak. Pyrochlore is the main Nb-bearing mineral within the aegirine carbonatite. However, its paucity in quartz-free feldspathic rocks, suggests the presence of minerals of the columbite series or fersmite, a possibility that remains to be tested by microprobe analysis. Projection of the Wolverine fault zone, probably the main Nb metallotect in the area, was shifted northeast to reflect results of a recent magnetic survey. Geochemical anomalies identified by Rara Terra Minerals Corp. at the Vergil carbonatite, less than 5 km northwest of the Lonnie complex, lie along the reinterpreted projection of the Wolverine fault. Keywords: Niobium, quartz-free feldspathic rocks, carbonatite, fenite, pyrochlore, columbite series minerals 1. Introduction Niobium (Nb) is a strategic metal that is mainly used for the production of steel and superalloys (e.g., Simandl et al., 2012). The global Nb supply for 2011 is estimated at 63 000 tonnes of contained Nb. Brazil (58 000 tonnes) and Canada (4400 tonnes) are the main producing countries (Papp, 2012). Carbonatites and their weathered equivalents are the main sources of Nb (Mariano, 1989a, b; Birket and Simandl, 1999; Simandl et al., 2012). Most carbonatites are found in stable cratonic settings, commonly along ancient rift zones (Wolley and Kjarsgaard, 2008; see Gwalani et al., 2010 and references therein for summaries of recent research on carbonatites and alkaline rocks). British Columbia carbonatite-related deposits straddle the western margin of ancestral North America, in the British Columbia alkaline province (Fig. 1, inset; Pell, 1994), which also hosts numerous other potential specialty metals deposits (Birkett and Simandl, 1999). In British Columbia, carbonatites and their host rocks have been affected by several periods of tectonic activity and overprinted by medium- to high-grade metamorphism. Niobium mineralization associated with the Lonnie metacarbonatite (MINFILE 093N 012) represents the third-most developed Nb prospect in British Columbia (after the Aley and Upper Fir deposits). The Lonnie deposit, the smallest of the three, lies 220 kilometres northwest of Prince George and approximately 7 kilometres east of the Manson Creek settlement (Fig. 1, inset). Discovered in 1953, Lonnie was stripped and drilled by Northwest Exploration Limited (Thompson, 1955; Hankinson, 1958). Since then it has been intermittently investigated by a number of individuals and companies (Vaillancourt and Payne, 1979). Currently, the deposit is being investigated by Rara Terra Minerals Corp, which recently conducted airborne geophysical and soil surveys (Helmel, 2012). This deposit was chosen as part of the specialty metals component of the 2012 Targeted Geoscience Initiative 4 (TGI4) because: 1) the paragenesis, mineralogy, and mineral chemistry of this complex has not been investigated by modern laboratory methods; and 2) much of the mineralization is considered to be in feldspar-rich lithologies, which contrasts with the Aley and Upper Fir deposits. The main objective of this component of TGI4 is to reduce the knowledge gaps currently hampering the exploration for, and development of, specialty metal deposits. This study describes the Geological Fieldwork 2012, B.C. Ministry of Energy, Mines and Natural Gas, British Columbia Geological Survey Paper 2013-1 127
Geological setting of the Lonnie niobium deposit, British Columbia, Canada
Jun 23, 2023
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